The invention relates to a process for the continuous fluidised bed agglomeration of a solid in powder form, which is sprayed together with a granulating liquid into a fluidised bed operated with fluidising gas, and in which the finished granular material is discharged out of the fluidised bed through a gas classifier.
To this end, the powder to be agglomerated is placed in the apparatus and transferred to the fluidised bed state by means of the fluidising gas. The fluidised powder is sprayed with the granulating liquid and thus brought to a sticky state with the result that granular product formation commences. If the grains of granular material have the desired size, drying generally takes place in the same apparatus with the liquid supply switched off.
In view of the constantly changing particle size of the powder until the finished granular material, the fluidising behaviour of the solid is subject to constant change, smaller particles in the fluidised bed requiring a lower fluidising velocity than large particles. For this reason, the fluidising velocity is usually adjusted to the particle size. A fluidising velocity that is too high leads to a discharge of product out of the bed; a fluidising velocity that is too low allows the bed to "collapse".